So this week i discovered that quite a few users were not receiving mails, and after digging around i realised that Mailgun has a few IP addresses that are blocked by some mail providers (Outlook and Hotmail are the ones i noticed). I've made the switch to Postmark (tell them i sent you for 1 month free!).
The difference i noticed immediately was delivery was faster and the tracking they use is very fluent so you can see whats going on at a glance. The email templating system they have is brilliant, i ditched my templates in Laravel and just use theres. I now have much better looking emails as well as perfect delivery.
Not really plugging these guys, but they are worth checking out if you experience the issues i had.